On 10/9/18 8:54 AM, Rob Landry wrote:
> 
> ...
> 
> rd.conf is set to run Rivendell as user 'scott'. I do this because it is
> easier to debug external scripts if Rivendell is running as the same
> user I log in as.
> 
> However, what I've just discovered is that the Bruins scripts are
> failing because they don't have permissions to access the serial port --
> even though user 'scott' is in the dialout group and does have such
> permissions.
> 

Hey Rob,

From what I know /etc/rd.conf doesn't actually specify the user ID under
which to run the daemons. On a CentOS installation the service daemons
(caed, ripcd, rdcatchd) run as user root. And in fact /usr/bin/caed is
normally configured to run SUID (set-user-id) by doing chmod u+s
/usr/bin/caed to make sure it runs as that user ('root' on CentOS).

> That means that at least part of Rivendell must be running as a user
> other than 'scott'. 'chmod o+rw /dev/ttyS0' cures the problem.
> 
> The obvious question is: what user is it running as? Since the scripts
> were working from the command line, 'scott' clearly had permissions to
> access the serial port.


Here's a Linux ps(1) alias I use to help understand the user ID's
process are running as (watch the text wrap, it's all on one line):

alias pss='/bin/ps -N --pid 2 --ppid 2 --format
pid,ppid,tty,user,group,wchan=-----------WCHAN-------------,%mem,%cpu,lstart,args
--sort start_time --forest'

> 
> I vaguely recall having encountered this problem before. This is RD 2.18
> running on Debian 8. There's no SELinux installed, so it can't be
> anything like that.
> 
> For now, I'm adding 'chmod o+rw /dev/ttyS0' to my startup script, as
> that seems to be an effective workaround; but I'd love to understand why
> the problem crpped up in the first place.

Long story short: I'd check ownership and permissions of /usr/bin/ripcd,
and the process owner for the running ripcd process.

Hope this helps a little!

  ~David Klann

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